Lab Med Qual Assur.  2021 Jun;43(2):72-79. 10.15263/jlmqa.2021.43.2.72.

Development and Stability Evaluation of In- House Prepared External Quality Controls for Autoimmune Disease Tests

Affiliations
  • 1Department of Laboratory Medicine, College of Medicine, The Catholic University of Korea, Seoul, Korea
  • 2Department of Laboratory Medicine, Jeonbuk National University Medical School, Jeonju, Korea
  • 3Research Institute of Clinical Medicine of Jeonbuk National University-Biomedical Research Institute of Jeonbuk National University Hospital, Jeonju, Korea

Abstract

Background
The control samples for external quality assessment (EQA) must be highly stable during the EQA process. This study aimed to evaluate the stability of in-house prepared external quality controls for autoimmune disease tests, including anti-nuclear antibody (ANA), anti-double stranded DNA immunoglobulin G antibody (anti-dsDNA), anti-thyroglobulin antibody (anti-Tg), and anti-thyroperoxidase antibody (anti-TPO).
Methods
The in-house prepared external quality controls with two different levels (negative and positive for ANA and anti-dsDNA; low and high for anti-Tg; and anti-TPO) for each autoimmune disease test were prepared and stored at test temperatures of –20℃, 4℃, and room temperature (RT). The levels of each autoimmune disease test were measured at baseline and at 1 week, 2 weeks, 1 month, 3 months, and 6 months. The internal quality controls from the same batch run were also tested during the evaluation period.
Results
The negative and positive controls for ANA were stable for 6 months, regardless of storage temperature. The positive control for anti-dsDNA tended to increase in level at 6 months (P =0.033). The low and high anti-Tg controls tended to decrease in levels at 3 months (P =0.033 and P =0.042, respectively). The low control of anti-TPO decreased in level at RT compared to –20℃ at 1 week (P =0.026) and the high anti-TPO controls tended to decrease in level at 3 months regardless of storage temperature such as –20℃, 4℃, and RT (P =0.041).
Conclusions
The stability of in-house prepared external quality controls was influenced by different storage temperatures and durations. These results indicate that all EQA samples for autoimmune disease tests should be stored at –20℃ or 4℃ and be tested as soon as possible during the EQA process.

Keyword

Stability evaluation; In-house prepared quality controls; External quality assessment; Autoimmune disease tests
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